Despite the announcement a few days ago, Jean MacKenzie, director of the Institute for War and Peace Reporting in Afghanistan, doesn't think a runoff vote is likely:
Chances are there will not be a second round; weather and logistics could easily combine to torpedo the effort, and the challenger Dr. Abdullah Abdullah has already hinted that he is open to talks “if winter should make a second round impossible.” A runoff is in no one’s interests. The Afghan people are tired and disgusted, and no second round is going to redeem the democratic process in their eyes. The turnout is likely be miniscule under 20 percent making any talk of government legitimacy more than a little absurd.
[...] The object of [Tuesday's] morality play was to force Mr. Karzai to acknowledge, at least tacitly, that he could not get away with the wholesale disregard for the law that he had shown throughout the election process.That accomplished, there is really no need to go the rest of the way. It would be expensive, dangerous, and chancy. Given an extremely low turnout in the south, Mr. Karzai could even lose, which would mean that his supporters would feel the need to resort to fraud, albeit a little more skillfully this time.